Drawing be-containing alloys



Patented Jan. 5, 1943 UNITED STATES PATENT OFFICE naawmc BE-OONTAININGarmors George H. Slagle, Temple, Pa., assignorto The BerylliumCorporation, Temple, Pm, a corporation of Delaware No Drawing.Application December 16, 1940,

Serial No. 370,351

2 Claims. (Cl- 20521) tubes from Be-containing alloys of one of themetals of the group containing Cu, Ni, Fe and Co. Thealloys commonlycontain from .10-4.0% beryllium with or without small percentages ofother associated alloying elements enhancing the precipitation hardeningproperties of the Be or the electrical and physical properties of theberyllium-containing alloy.

Another object is to facilitate the production of wire, rod and tubulararticles from said alloys. Still another object is toimprove the drawingproperties of said alloys. Other objects and advantages will be apparentas the invention is more fully hereinafter disclosed.

In accordance with these objects, I have discovered that the excessivedie wear ordinarily encountered in the drawing of the said alloys andoccasioned either by the presence of metal oxide or of berryllidecompounds on the surface of said alloys is efiectively eliminated bycoating the alloy surface with a relatively thin film of a relativelysoft metallic lubricant consisting of one of the group of metals Cd, Ag,Sn, Zn and Pb.

The thickness of the metallic lubricating film provided on theBe-contaim'ng alloys in accordance with the present invention may varywidely without essential departure therefrom, as one skilled in the artwill perceive, depending upon the specific metallic lubricant employedand upon the specific alloy being drawn. In general the thickness of thefilm should be no more than is required to provide the desiredlubrication initially, and an extension of the film over the entireelongated length of the alloy subsequently to drawing. Film thicknessessufficient to provide a drawing sheath for the alloy however are notwithin the scope of the present invention.

As one specific embodiment of the present invention, but not as alimitation theerof, the adaptation of the same to a metallic lubricatingfilm comprised of cadmium in the drawing of copperberyllium alloyscontaining from .104.0% beryllium will be described. I have found thatfor the purposes of the present invention a cadmium film ranging from aminimum thickness of about .00001 inch to a maximum of about .0002 inchis a satisfactory metallic lubricating film in the drawing ofcopper-beryllium alloys. In general the thickness of the cadmium filmprovided may vary within this thickness range with respect to the extentof elongation to be applied to the alloy in one or more drawing passes.In general, a thickness of about .00001 inch is sufllcient to providelubrication of most Cu.Be alloys during a reduction in area of up to ashigh as 70%, al-

though preferably the total reduction in area would not exceed about50%.

As hereinabove indicated, the cadmium film thickness should be no morethan is necessary to provide surface lubrication over the entireextended length of the alloy being drawn. Accordingly with any givendegree of elongation per pass there is a minimum initial film thicknessto accomplish this result. Any film thickness over this minimum filmthickness is undesired for the purpose of the present invention,although cadmium film thicknesses up to .0002 inch may generally beemployed without deleterious results particularly in the larger sizedrods and wires. In the drawing of copper-beryllium alloys, however, thealloy is subjected to a plurality of separate drawing passes each passreducing the crosssectional area a determined percent, the total numberof said separate passes being calculated to accomplish a determinedtotal percent reduction in area before the work hardeningcharacteristics of the alloy are increased to' an extent inhibitingfurther cold mechanical deformation. Under these conditions, therefore,the cadmium film thickness must be at least sufilcient to provide for anextension of the metallic lubricating film cover the total extendedlength obtained in the plurality of drawing passes.

I have found that a cadmium film thickness not in excess of about .0002is about the maximum permissible lubricating thickness on the surface ofany copper-beryllium alloy capable of being subjected to cold mechanicaldeformation by drawing thesame through a die. Thicknesses in excessof'this thickness tend to strip off and to clog up the die opening.

I have found that a cadmium film thickness of about .0001 inch is aboutthe most satisfactory thickness to apply generally to allcopper-beryllium alloys containing beryllium within the range specifiedto provide sufilcient metallic lubricant for 'a total reduction in areain a plurality of drawing operations of between 40 to In the practice ofthe present invention, the copper-beryllium alloy at the conclusion ofthe hot working operation and when at a rod diameter of about .750 inchis first subjected to a high temperature heating followed by a rapidcooling operation heretofore customarily applied thereto to conditionthe alloy for cold mechanical treatment. The surface of the alloy thenis thoroughly cleaned of surface scale and oxides and the cleaned metalsurface then is coated with an adherent film'of cadmium to a thicknessnot in excess of about .0002 inch.

This cadmium film coating may be applied in a plurality of ways withoutessential departure from the present invention. The more firmly adherentthe film to the surface of the alloy the better the film is for thepurposes of the present invention. Film coatings obtained by immersionor deposition plating are preferred. Film coatings obtained byelectro-deposition, however, are generally satisfactory for the purposesof the present invention where the current densities employed aresufllcient to produce the desired film adherence. Film thicknessesobtained by dipping in a molten metal bath when accompanied by partialsurface alloying of the cadmium with the copper appear equally aseffective as those obtained by immersion or deposition plating.

Following the surfacing of the alloy with the cadmium film to thedesired thickness the subsequent cold drawing of the alloy isaccomplished in a manner heretofore well known in the art, with theadvantage that by the use of the metallic lubricant the copper-berylliumalloys may be drawn at greater speed rates through the die and inconsiderably greater quantities than heretoi'ore possible and moreovercan be given considerably larger percent reductions in area before thework hardening effects require annealing before further cold reductionscan be applied.

As an example of this improvement, copperberyllium alloys containingabout 2% Be ordinarily require about eight (8) anneals during reductionof the same from a size approximating .750 inch to a size approximating.032 inch. On surfacing the alloy with cadmium 'to a film thickness notin excess of about .0002 inch but preferabhr to a film thicknessapproximating .0001 inch, I have found that only about anneals arenecessary and that I can cold reduce the alloy between 40% and 65%reduction in area in a plurality of separate drawing operations betweeneach anneal.

As an example of the efflciency of the cadmium lubricant in the drawingof copper-beryllium alloys, wire comprised of copper-beryllium andcontaining Be about 2% when reduced in diameter from .155 inch to .125inch, a reduction in area of about 35%, without such a metalliclubricant will destroy the die size of a tungsten carbide die beforemore than 10 pounds of the wire has been drawn therethrough. With ametallic lubricant and at drawing speeds as high as about 156 feet perminute up to 300 pounds of the wire may be drawn through the die withoutdeleterious eflect upon the die size.

The advantage of the present invention is more marked in multiple diedrawing of Cu.Be alloys. For example, considerable difilculty heretoforehas been experienced in the multiple die drawing of Cu.Be alloys of thesmaller sizes where higher drawing speeds are desired of around 500 feetper minute. Ordinarily without the metallic lubricant of the presentinvention only about 1 to 2 pounds of a Cu.Be alloy containing about 2%Be can be drawn before one or more of the dies is deleteriouslyaffected. By the practice of the present invention and with an initialcadmium thickness of about .0001 inch, for example, between 300 to 500pounds ofwire may be drawn, for example, from a wire size of about .032inch to a wire size of about .016 inch through a plurality of dies eachgiving the wire about a 25% reduction in area, at drawing speeds as highas 500 feet per minute without deleteriously affecting the plurality ofdie sizes.

The two examples above given indicate the marked economic advantagegained by the practice of the present invention. When diamond dies areemployed the advantage of the present inventionis still more marked, forexample, under the same circumstances given in the paragraph above over1000 pounds of the wire may be drawn as contrasted to less than 200pounds without the metallic lubricant.

The above noted drawing results are characteristic of those obtainablewith all copper-beryllium alloys containing beryllium .10-4.0% by thepractice of the present invention. The lower beryllium content alloysappear to draw more easily than the higher beryllium content alloys,

eating film described.

In general, the film thickness employed in the drawing of these alloysis the same as that found most suitable for the higher Be content copperalloys. Nickel-beryllium alloys, for example, are exceedingly difilcultto draw commercially due to excessive strain on the draw head and veryserious die wear. By the practice of the present invention the drawingof these alloys is materially simplified and rendered commerciallypractical.

Whereas, hereinabove I have described the present invention giving themetal cadmium as a specific example of the metallic lubricant employed,it is believed apparent that other metals may be employed for suchpurpose without essential departure therefrom such as, for example, tin,lead, zinc, silver and copper, which for the purpose of the presentinvention are to be considered substantial equivalents for cadmium.

The precise film thicknesses of these metals eifective as lubricatingfilm will vary from that thickness hereinabove indicated as being properfor cadmium as one skilled in the art will perceive. The lubricatingproperties of tin appear to be closely approximate that of cadmium andfilm thicknesses of tin approximating that hereinabove given for cadmiumare equally as good for the purposes of the present invention.

Having hereinabove broadly and specifically described the presentinvention and given one specific embodiment of the same, it is believedapparent that many modifications may be made therein without essentialdeparture therefrom and all such are contemplated as may fall within thescope of the following claims.

What I claim is:

1. In the cold drawing of copper-beryllium alloys containing from.10-4.0% Be from rod to wire size, the improvement which comprisessurfacing the rod with an adherent relatively thin coating of cadmiumnot exceeding about .0002 inch in thickness.

2. The method of eliminating excessive die wear and drawhead strain inthe cold drawing of wire comprised of an alloy of copper containing from.10-4.0% Be which comprises surfacing the wire prior to drawing with arelatively thin film of a metallic lubricant consisting of cadmium, thethickness of said film being not in excess of about .0002 inch.

GEORGE E. SLAGLE.

